The present invention relates to high temperature sensors and more particularly, to a method which enables the fabrication of a specifically selected single crystal 3Cxe2x80x94SiC layer located on, and dielectrically isolated from, an independently selected 6Hxe2x80x94SiC substrate or any other type of SiC substrate material.
As one will ascertain, pressure transducers capable of operating at high temperatures of at least, for example 600xc2x0 C. and being physically small are highly desirous in various applications. When temperatures reach levels above 600xc2x0 C., silicon-sensing networks and silicon force collectors undergo significant plastic deformation rendering the device useless as a pressure transducer. In order to overcome this problem, high temperature transducers employing SiC have been fabricated. For example, see U.S. Pat. No. 5,165,283 to A. D. Kurtz et al. entitled, xe2x80x9cHigh Temperature Transducers and Methods of Fabricating Same Employing SiCxe2x80x9d assigned to the assignee herein, Kulite Semiconductor Products, Inc. Also see, for example, U.S. Pat. No. 6,058,782 entitled, xe2x80x9cHermetically Sealed Ultra High Temperature SiC Pressure Transducers and Method for Fabricating the Samexe2x80x9d issued to A. D. Kurtz et al. on May 9, 2000 and also assigned to the assignee herein. Thus, there is a desire to fabricate high temperature transducers.
The present invention enables the fabrication of a specifically selected (both the type and the doping) single crystal 3Cxe2x80x94SiC layer located on, and dielectrically isolated from an independently selected 6Hxe2x80x94SiC substrate, or any other SiC substrate material.
The device thus produced using this approach will have the benefit of having an excellent single crystal 3Cxe2x80x94SiC, on an insulator layer with specified doping for piezoresistive sensing while having an independently selected substrate material like 6Hxe2x80x94SiC or 4Hxe2x80x94SiC used for producing the deflecting membrane or other substrate.
Semiconductor devices useful in high temperature sensing applications include a silicon carbide substrate, a silicon dioxide layer, and an outer layer of crystalline doped silicon carbide. The device is a 3Cxe2x80x94SiC/SiO2/SiC structure. This structure can be employed to fabricate high temperature devices such as piezoresistive sensors, minority carrier devices and so on. The crystalline doped silicon carbide is dielectrically isolated from the substrate. The devices are formed by processes that include bonding a pattern wafer to a substrate wafer, selective oxidation and removal of undoped silicon, and conversion of doped silicon to crystalline silicon carbide. The level of doping and the crystalline structure of the silicon carbide can be selected according to desired properties for particular applications.